Fluid pressure control circuit and work machine

Abstract

To provide a fluid pressure control circuit capable of improving fuel consumption performance while improving responsiveness to an operation input, and a work machine including the same.SOLUTION: A controller 35 has a function of controlling a confluence valve 31 to an open position on the basis of detection of a standby state in which a spool valve 14 is in a non-operation state from an idling state in which a plurality of hydraulic pumps 12 are activated, controlling any one of bypass valves 27 to the open position, controlling the remaining other bypass valves 27 to a closed position, controlling a discharge flow rate of any one of the hydraulic pumps 12 to a required flow rate for generating a standby pressure, and controlling the discharge flow rate of the remaining other hydraulic pumps 12 to the required flow rate or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fluid pressure control circuit for controlling a pump discharge pressure, and a work machine equipped with the same. [Background technology]

[0002] Conventionally, a hydraulic circuit configuration equipped with two variable displacement main pumps has been known for use in work machines such as hydraulic excavators. In this configuration, bypass valves are provided corresponding to the hydraulic circuits to which each pump supplies hydraulic oil, and when a transition from an idling state in which the main pump is started and the hydraulic lock lever is in the locked position to a standby state in which the hydraulic lock lever is in the unlocked position and the operating lever is not operated is detected, a fixed amount of hydraulic oil is passed through each bypass valve to generate back pressure (standby pressure), thereby improving the responsiveness of the hydraulic actuator when the lever operation begins.

[0003] That is, in this configuration, the discharge flow rate of each of the two pumps is controlled, and the discharged hydraulic oil is returned to the tank via the bypass valve corresponding to each pump, thereby generating standby pressure in the hydraulic circuit of each pump (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5622243 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in terms of fuel economy, low flow and low pressure are desirable for pump control in idling and standby states. In the case of the above control, the flow rate required to generate standby pressure is discharged from each of the two pumps, so a configuration that further improves fuel economy is desired.

[0006] The present invention has been made in consideration of the above points, and has as its object to provide a fluid pressure control circuit that can improve responsiveness to operational inputs while also improving fuel efficiency, and a work machine equipped with the same. [Means for solving the problem]

[0007] The fluid pressure control circuit of the present invention is a fluid pressure control circuit in which working fluid in a tank is discharged to each pump discharge passage by a plurality of variable displacement fluid pressure pumps, supplied to a fluid pressure actuator under control of a control valve, and returned to the tank, and is equipped with return passages that communicate each pump discharge passage with the tank, bypass valves that open and close each of these return passages, communication passages that communicate between the pump discharge passages, a merging valve that opens and closes this communication passage, and a controller that controls the opening and closing of each bypass valve and the merging valve, and the controller has the function of controlling the merging valve to an open position, controlling one of the bypass valves to an open position, and controlling the remaining bypass valves to a closed position, thereby controlling the discharge flow rate of one of the fluid pressure pumps to a flow rate required to generate standby pressure, and controlling the discharge flow rate of the remaining fluid pressure pumps to be equal to or less than the required flow rate, based on detection of a transition from an idling state in which the plurality of fluid pressure pumps are started to a standby state in which the control valves are not operated. [Effects of the Invention]

[0008] According to the present invention, it is possible to improve fuel efficiency while improving responsiveness to operational inputs. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a circuit diagram showing an embodiment of a fluid pressure control circuit according to the present invention; [Figure 2] FIG. 4 is a circuit diagram showing the standby state of the fluid pressure control circuit. [Figure 3] 4 is a flowchart showing the control of a controller used in the fluid pressure control circuit. [Figure 4] FIG. 2 is a side view showing a working machine equipped with the same fluid pressure control circuit. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below based on an embodiment shown in FIGS.

[0011] In Fig. 4, reference numeral 1 denotes a work machine. In this embodiment, a hydraulic excavator is taken as an example of work machine 1. Work machine 1 comprises a machine body 4 in which an upper rotating body 3 is rotatably mounted relative to a lower traveling body 2, and upper rotating body 3 is mounted with a work implement (front working implement) 5 and a cab 6 that surrounds a cab in which an operator sits. Inside cab 6, operating units such as levers or pedals operated by the operator are arranged, and operation of the operating units causes travel by the lower traveling body 2, rotation by the upper rotating body 3, and work by the work implement 5, etc. to be performed.

[0012] The work machine 1 is equipped with a fluid pressure control circuit 10. In this embodiment, as shown in Fig. 1, the fluid pressure control circuit 10 supplies hydraulic oil, which is a working fluid, in a tank 13 by means of a plurality of, for example, two hydraulic pumps (main pumps) 12 driven by the on-board engine to a plurality of spool valves 14 arranged together as control valves, and controls the direction and flow rate of the hydraulic oil by the displacement direction and displacement amount of these spool valves 14, so that the hydraulic oil is supplied to hydraulic actuators 15, which are a plurality of fluid pressure actuators for operating operating parts. Note that while the hydraulic actuators 15 are shown as hydraulic cylinders by way of example, hydraulic motors and the like are also included in the hydraulic actuators 15.

[0013] In such a hydraulic circuit, the various spool valves 14 are operated in response to the operation of an operating unit. The illustration shows an example of electrical control in which the operating unit is an electric joystick and is controlled in response to an electrical signal output from the operating unit, but the spool valves 14 may also be hydraulically pilot operated by a pilot pressure output via a pilot valve in response to the operation of the operating unit.

[0014] The load circuit is roughly divided into two circuits corresponding to the two hydraulic pumps 12. For clarity of explanation, the drawing representatively shows one spool valve 14 and one hydraulic actuator 15 for each circuit, but each circuit may be provided with a plurality of spool valves 14 and hydraulic actuators 15.

[0015] A pump discharge passage 21 is connected to each hydraulic pump 12. A relief valve may be provided in a return passage between each pump discharge passage 21 and the tank 13 so that hydraulic oil exceeding the set pressure of the relief valve is returned to the tank 13.

[0016] Furthermore, a return passage 25 is connected between each pump discharge passage 21 and the tank 13. A bypass valve 27 is provided in each return passage 25. These bypass valves 27 are, for example, spool-type two-port throttle switching valves that can be proportionally controlled between a position where the opening area is maximum, i.e., a fully open position (open position) 27a, and a position where the opening area is minimum, i.e., a fully closed position (closed position) 27b. That is, each bypass valve 27 controls the amount of communication through each return passage 25 in accordance with its opening area. In this embodiment, an example of an electromagnetic proportional valve is shown as the bypass valve 27, but a pilot-operated valve may also be used.

[0017] Furthermore, the pump discharge passages 21, 21 are communicated with each other via a communication passage 30. A junction valve 31 is provided in this communication passage 30. The junction valve 31 joins the pump discharge passages 21 of the multiple hydraulic pumps 12 to merge the circuits, and is also called a combiner valve. The junction valve 31 is a switching valve that can be switched between a position (open position) 31a where the opening area is maximum, i.e., a fully open position, and a position (closed position) 31b where the opening area is minimum, i.e., a fully closed position. In other words, the junction valve 31 controls the amount of communication through the communication passage 30 depending on its opening area. In this embodiment, an example of the junction valve 31 is shown as a solenoid valve, but it may also be a pilot-operated valve.

[0018] The bypass valve 27 and the junction valve 31 may be provided together with the spool valve 14 as a control valve.

[0019] The fluid pressure control circuit 10 is also provided with a locking means that must be operated by the operator of the work machine 1 (Figure 4) before operating the control unit. The locking means may be, for example, a circuit or switch for limiting or blocking the transmission of an electrical signal from the control unit to the spool valve 14, or a valve such as a safety check valve provided in the hydraulic circuit. The locking means is switched between locked and unlocked in response to the operator's operation of a locking operation unit, such as a hydraulic lock lever or switch, located in the cab 6 (Figure 4). Unless the locking means is in the unlocked state, the work machine 1 (Figure 4) cannot be moved, even if the on-board engine is started to operate the hydraulic pump 12 and the operator operates the control unit.

[0020] Each hydraulic pump 12 is a variable displacement pump in which a displacement varying means such as a swash plate is controlled by a regulator 36 which is operated by a control electromagnetic proportional valve which receives a control signal sent from a controller 35, and each discharge flow rate can be variably adjusted proportionally from the minimum flow rate under no load according to the load.

[0021] A signal corresponding to the operation of the operating unit is input to the controller 35. For example, if the operating unit is an electric joystick, the signal corresponding to the operation of the operating unit is an operation signal output directly or indirectly from the operating unit, or if the operating unit is operated by a hydraulic pilot, a signal indicating the pilot pressure detected by a pressure sensor or the like. In addition, a detection signal from a detection unit that detects that the locking means has been released and safety has been confirmed is input to the controller 35.

[0022] Furthermore, the controller 35 outputs control signals to each of the bypass valves 27 and the merging valve 31. In this embodiment, each of the bypass valves 27 and the merging valve 31 is a solenoid valve, and an example is shown in which the controller 35 sends control signals directly to the solenoids of each of the bypass valves 27 and the merging valve 31, but this is not limiting. If each of the bypass valves 27 and the merging valves 31 is a pilot-type valve, an electro-hydraulic converter valve may be used to convert the control signal output from the controller 35 into a pilot pressure to control each of the bypass valves 27 and the merging valve 31.

[0023] In this embodiment, the state in which the locking means is not released even when the vehicle engine is started and the hydraulic pump 12 is activated is defined as the idling state, the state in which all operating parts, i.e., spool valves 14, remain in a non-operating state even after the locking means is released is defined as the standby state, and the state in which the locking means is released and any operating part, i.e., spool valve 14, is operated is defined as the operating state.

[0024] In an idling state, as shown in FIG. 1, the controller 35 controls the junction valve 31 to a position 31b where the opening area is minimum, i.e., where it is fully closed, thereby isolating the circuits of the hydraulic pumps 12, and controls each bypass valve 27 to a position 27a where the opening area is maximum, i.e., where it is fully open, while maintaining the discharge flow rate of each hydraulic pump 12 at a minimum flow rate by a regulator 36 operated by a control electromagnetic proportional valve.

[0025] Furthermore, when the controller 35 receives a detection signal from the detector that indicates the release of the locking means from an idling state and switches to a standby state, as shown in Fig. 2, it controls the junction valve 31 to a fully open position 31a, thereby connecting the circuits (pump discharge passages 21) of the multiple hydraulic pumps 12 via the communication passage 30, and sets one bypass valve 27 to a fully open position 27a where the opening area is maximized, i.e., a fully open position, and sets the other bypass valve 27 to a fully closed position 27b where the opening area is minimized, i.e., a fully closed position, thereby increasing the back pressure (standby pressure) of the hydraulic pumps 12. At this time, the controller 35 sets the discharge flow rate of one hydraulic pump 12 according to the opening area of ​​the other bypass valve 27 using a regulator 36 operated by a control electromagnetic proportional valve so as to be the flow rate required to generate the required standby pressure, and maintains the discharge flow rate of the other hydraulic pump 12 at or below the required flow rate, for example, a minimum flow rate, using the regulator 36 operated by a control electromagnetic proportional valve.

[0026] In the drawings, the left hydraulic pump 12 is described as one hydraulic pump 12 and the right hydraulic pump 12 is described as the other hydraulic pump 12, but these may be reversed. Similarly, the left bypass valve 27 corresponding to the left hydraulic pump 12 is described as one bypass valve 27, and the right bypass valve 27 corresponding to the right hydraulic pump 12 is described as the other bypass valve 27, but these may be reversed. Furthermore, the hydraulic pump 12 corresponding to one hydraulic pump 12, the hydraulic pump 12 corresponding to the other hydraulic pump 12, the bypass valve 27 corresponding to one bypass valve 27, and the bypass valve 27 corresponding to the other bypass valve 27 do not always need to be the same.

[0027] Furthermore, when the controller 35 transitions from the standby state to the operating state in which the operating unit, i.e., the spool valve 14, is operated, the controller 35 controls the junction valve 31 to a position 31b where the opening area is minimum, i.e., where the junction valve 31 is fully closed, thereby isolating the circuits of the hydraulic pump 12, and controls the discharge flow rate of the hydraulic pump 12 to increase in accordance with an increase in the amount of operation of the operating unit, i.e., the spool valve 14, and controls the bypass valve 27 to a position where the opening area is reduced in accordance with an increase in the amount of operation.

[0028] The above control will be explained with reference to the flowchart shown in FIG.

[0029] (Step 1) The controller 35 determines whether or not the engine is in an idling state based on the input signal from the operation unit and the detection signal from the detection unit.

[0030] (Step 2) When there is no input signal from the operating unit or a detection signal from the detecting unit, the controller 35 determines that the hydraulic pump 12 is in an idling state in which no safety confirmation operation is performed even if the hydraulic pump 12 is operating, and therefore controls the junction valve 31 to a fully closed position 31b using a control signal from the controller 35, controls the discharge flow rate of the hydraulic pump 12 to a minimum using a regulator 36 operated by an electromagnetic proportional valve that has received a control signal from the controller 35, and controls the bypass valve 27 to a fully open position 27a using a control signal from the controller 35.

[0031] (Step 3) If the controller 35 determines in step 1 that the vehicle is not in an idling state, it determines whether the vehicle is in a standby state or not based on the input from the operation unit and the detection signal from the detection unit.

[0032] (Step 4) If there is no input signal from the operating unit but a detection signal from the detecting unit, the controller 35 determines that the spool valve 14 is in a standby state in which it is not operated even after the safety confirmation operation has been performed, and therefore controls the merging valve 31 to a fully open position 31a using a control signal from the controller 35, controls one bypass valve 27 to a fully open position 27a using a control signal from the controller 35, and controls the discharge flow rate of one hydraulic pump 12 in accordance with the opening area of ​​one bypass valve 27 using a regulator 36 operated by an electromagnetic proportional valve that has received a control signal from the controller 35. Also, controls the other bypass valve 27 to a fully closed position 27b using a control signal from the controller 35, and controls the discharge flow rate of the other hydraulic pump 12 to a minimum using a regulator 36 operated by an electromagnetic proportional valve that has received a control signal from the controller 35.

[0033] (Step 5) If the controller 35 determines in step 1 that the engine is not in an idling state and in step 3 that the engine is not in a standby state, it determines whether the engine is in an operating state or not from the input signal of the operating unit and the detection signal of the detection unit.

[0034] (Step 6) When there is an input signal from the operating unit and a detection signal from the detection unit, the controller 35 detects the operating state in which the spool valve 14 has been operated in addition to the unlocking operation of the locking means, and therefore controls the discharge flow rate of the hydraulic pump 12 to increase in accordance with an increase in the amount of operation of the operating unit, i.e., the spool valve 14, and controls the opening area of ​​the bypass valve 27 to a position where it decreases in accordance with an increase in the amount of operation of the operating unit, i.e., the spool valve 14.

[0035] In this way, when the controller 35 detects an idling state in which the hydraulic pump 12 is operating but no safety confirmation operation is performed, it controls the merging valve 31 to position 31b where it is fully closed, controls the discharge flow rate of the hydraulic pump 12 to a minimum, and controls each bypass valve 27 to position 27a where it is fully open, thereby eliminating pump back pressure during idling and improving fuel efficiency. Furthermore, when the controller 35 detects a standby state in which all spool valves 14 are not operated even after the safety confirmation operation has been performed, it controls the junction valve 31 to position 31a where it is fully open, controls one bypass valve 27 to position 27a where it is fully open, and controls the other bypass valve 27 to position 27b where it is fully closed, thereby controlling the discharge flow rate of one hydraulic pump 12 to a flow rate required to generate standby pressure, and controlling the discharge flow rate of the other hydraulic pump 12 to not more than the required flow rate, preferably less than the required flow rate, for example, to a minimum flow rate, thereby suppressing the discharge flow rates of hydraulic pumps 12 other than the hydraulic pump 12 whose discharge flow rate is adjusted to generate standby pressure, and returning the discharged hydraulic oil to the tank 13 only via one bypass valve 27. In other words, the standby pressure in the hydraulic circuit systems of both hydraulic pumps 12 is ensured by the discharge flow rate of only one hydraulic pump 12. Therefore, it is possible to generate standby pressure in each hydraulic pump 12 while reducing the total pump discharge flow rate, so that the pump discharge pressure can be appropriately controlled to improve responsiveness when an operation input is received from the standby state, while suppressing hydraulic energy consumption and improving fuel efficiency. In particular, in a configuration using two hydraulic pumps 12, in this embodiment, during standby, only the discharge flow rate of one hydraulic pump 12 is used and the discharge flow rate of the other hydraulic pump 12 can be set to a minimum flow rate, so that it is possible to generate standby pressure in the same way even if the total pump discharge flow rate is reduced to about half of the conventional example in which the discharge flow rates of the individual hydraulic pumps 12 are used.

[0036] Furthermore, it is possible to provide a work machine 1 that can eliminate pump back pressure during idling, suppress hydraulic energy consumption during standby, improve fuel efficiency, and improve responsiveness when an operation input is made from standby.

[0037] This control circuit allows the hydraulic pump 12 to achieve minimum flow rate and zero back pressure when idling, improving idling fuel economy to the utmost, and even when in standby mode, by setting one of the hydraulic pumps 12 to a minimum flow rate and applying standby pressure to each hydraulic pump 12 using only one of the bypass valves 27, good fuel economy can be achieved, and responsiveness can be improved even if the pressure and flow rate rise instantaneously in response to lever operation input, because the pump discharge pressure is already at a certain level or higher.

[0038] While the above embodiment has shown an example in which there are two hydraulic pumps 12, the present invention is not limited to this and can be applied to a case in which there are three or more hydraulic pumps 12. In that case, in the standby state, the junction valve 31 is controlled to an open position, one of the bypass valves 27 is controlled to an open position, and the remaining other bypass valves 27 are controlled to a closed position, thereby controlling the discharge flow rate of one of the hydraulic pumps 12 to a flow rate required to generate standby pressure, and controlling the discharge flow rate of the remaining other hydraulic pumps 12 to be equal to or lower than the required flow rate, thereby achieving the same advantageous effects. [Industrial Applicability]

[0039] The present invention has industrial applicability to those who manufacture and sell the above-mentioned fluid pressure control circuit and the working machine equipped with this control circuit. [Explanation of symbols]

[0040] 1. Work machinery 4 aircraft 10 Fluid pressure control circuit 12 Hydraulic pump, which is a fluid pressure pump 13. Tank 14 Spool valve as a control valve 15 Hydraulic actuator, which is a fluid pressure actuator 21 Pump discharge passage 25 Return Passage 27 Bypass valve 30 Communication path 31 Confluence valve 35 Controller

Claims

1. A fluid pressure control circuit in which a working fluid in a tank is discharged to a pump discharge passage by a plurality of variable displacement fluid pressure pumps, and is supplied to a fluid pressure actuator under control of a control valve, and is returned to the tank, return passages communicating each pump discharge passage with the tank; Bypass valves that open and close these return passages, respectively; a communication passage that communicates between the pump discharge passages; a junction valve that opens and closes this communication passage; a controller for controlling opening and closing of each bypass valve and each merging valve; The controller has a function of controlling the merging valve to an open position, controlling one of the bypass valves to an open position, and controlling the remaining other bypass valves to a closed position based on detection of a transition from an idling state in which the multiple fluid pressure pumps are activated to a standby state in which the control valves are not operated, thereby controlling the discharge flow rate of one of the fluid pressure pumps to a required flow rate for generating standby pressure, and controlling the discharge flow rates of the remaining other fluid pressure pumps to a required flow rate or less. A fluid pressure control circuit comprising:

2. The controller has a function of controlling the merging valve to a closed position while the plurality of fluid pressure pumps are running and idling, controlling the discharge flow rate of each fluid pressure pump to a minimum, and controlling each bypass valve to an open position.

2. The fluid pressure control circuit according to claim 1.

3. The controller has a function of controlling the merging valve to a closed position based on detection of an operating state in which the control valve has been operated from a standby state, increasing the discharge flow rate of the fluid pressure pump in response to an increase in the operating amount, and controlling the opening area of ​​the bypass valve to a position that decreases in response to an increase in the operating amount.

3. The fluid pressure control circuit according to claim 1 or 2.

4. The aircraft and The operating unit installed on this aircraft, a fluid pressure control circuit according to claim 1 that operates the operating unit; A work machine comprising:

Images